Why Is My Website Down?
A
Most outages trace back to one of six causes: a DNS problem, an expired domain, an expired TLS certificate, the host or server itself being down, a deploy that broke something, or an upstream provider (DNS host, CDN, cloud region) failing. Here they are, ordered roughly by how often each one actually happens.
1. DNS problems
DNS is the most common cause because it's the easiest thing to accidentally break: a changed record, an expired DNS provider account, or a typo in a nameserver setting can point your domain at nothing. The server itself can be perfectly healthy and still be unreachable. A DNS check that runs on a schedule catches a bad record within minutes of the change, instead of when a customer reports it.
2. An expired domain
Domains lapse when a renewal payment fails, an old card expires, or a reminder email lands in spam. Once the registration expires, the site — and its email — go dark, and restoring it can take days. Monitoring domain expiry is worth having even if you monitor nothing else, because there's no gradual warning: the domain works until the exact day it doesn't.
3. An expired TLS certificate
Certificates auto-renew until the automation quietly stops working — a failed renewal job, a DNS change that breaks domain validation, or a billing issue with the certificate authority. Once it expires, browsers block the page outright rather than showing a warning. A TLS check that alerts weeks before expiry, not the day of, is the difference between a routine renewal and an emergency.
4. The host or server is down
Sometimes it really is the simplest explanation: the server crashed, ran out of disk space or memory, or the hosting account was suspended. This is the failure an outside-in uptime check is built for — it hits the homepage on a schedule and knows within minutes if it stops responding, rather than waiting for someone to notice.
5. A deploy broke something
A bad deploy doesn't always return an error page — it can return a normal-looking 200 status with a broken page, a missing asset, or a crash loop that only shows up under real traffic. Monitoring that checks the response itself, not just the status code, catches this class of failure that a human might not notice for hours.
6. An upstream provider failure
Your DNS host, CDN, cloud region, or a third-party API you depend on can go down without anything changing on your end. These are the hardest to diagnose from the inside, because your own systems look fine — which is exactly why an outside-in check, run from probe locations separate from your infrastructure, is the fastest way to tell "it's not just me" from "it's not just them."
What's the most common reason a website goes down?
DNS problems are the most frequent cause — a changed record or an expired DNS account can make an otherwise healthy site unreachable.
Can a website go down because the domain expired?
Yes. If a domain registration lapses — often from a failed renewal payment — the site and its email both go dark until it's restored, which can take days.
Does an expired TLS certificate count as the site being down?
Functionally, yes. Browsers block pages with an expired certificate outright, so visitors experience it exactly like an outage even though the server is running fine.
How do I know if it's my host or my code?
An outside-in check that also inspects the response content — not just the status code — can tell the difference: a host outage fails to respond at all, while a bad deploy often still returns a 200 with broken content.
Why would my site be down if I didn't change anything?
An upstream provider — your DNS host, CDN, or cloud region — can fail independently of anything you did. It's the hardest cause to diagnose from the inside, which is why checking from outside your own infrastructure matters.
How can I catch these before customers do?
Continuous outside-in monitoring with alerts for TLS and domain expiry, DNS changes, and response content — not just a single ping — catches most of these causes before they turn into a support ticket.
Holter watches this for you: outside-in monitors plus dead-man heartbeats for silent failures. Free plan: 5 monitors, 5-minute checks, no credit card.
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